TUFLOW Remapping: Difference between revisions
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With the release of TUFLOW 2020, the combination of Quadtree mesh and Sub-grid Sampling (SGS) method has offered great flexibility to build a model with a range of mesh sizes. SGS samples the digital elevation model (DEM) at a number of points within a cell and computing the water surface elevation as a function of cell stored volume. With SGS, cells and faces can be considered as "partially wet", and this means the impact of the sub-grid scale geometry can be represented by cells with larger sizes. The example below shows a Quadtree model with 10/20m cell size can conduct water as smoothly as a 2.5/5/10/20m model along a narrow stream.<br>
[[File:Fig1 H sgs.png|700px]]<br>
'''Figure 1 Water level simulation results with SGS. Lefe: 2.5/5/10/20m Quadtree model. Right: 10/20m Quadtree model.'''<br><br>
On the other hand, the same model running without SGS method creates significant difference in the distance of water travelled along the gully.<br>
[[File:Fig2 H nonsgs.png|700px]]<br>
'''Figure 2 Water level simulation results without SGS. Lefe: 2.5/5/10/20m Quadtree model. Right: 10/20m Quadtree model.'''<br><br>
However, this has also create a need to "remap" the water level in large Quadtree cells to a DEM with much finer resolution. While we are developing high resolution SGS output in the future release, we have also added a new functionality in the [[ASC_to_ASC|ASC_to_ASC]] utility to remap a water level grid to a finer DEM grid. This page introduce how to use the ASC_to_ASC remap function, and also discuss the limitation of the method.▼
This means the mesh size sensitivities of a SGS model are significantly reduced, and modeller are increasingly using coarser mesh at model domain far away from the location of interest. However, this has also create a challenge on how to output water depth at those coarse cells. The example below shows even through the 10/20m mesh and the 2.5/5/10/20m mesh models produce similar water level, but the depth map output is much 'smoother'in the model with finer meshes. <br>
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=Base Case=
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